1. Field of the Invention
This invention relates to a new and improved training projectile that has a predetermined range limited trajectory characteristic. More particularly, radially distributed flats induce the onset of gyroscopic instability at a predetermined range, thereby reducing the overall flight path of the projectile.
2. Description of the Art
U.S. Pat. No. 4,063,511 (Bullard) discloses a spinning shotgun projectile with grooves to streamline the projectile body thereby decreasing air resistance during flight.
U.S. Pat. No. 4,520,972 (Diesinger et al.) discloses a spin-stabilized training projectile, which changes its axial stability by operation of a stabilizer mounted at the rear end of the projectile.
U.S. Pat. No. 4,708,065 (Schilling et al.) discloses a training projectile with an annular recess around its circumference but does not use roll damping to truncate the normal trajectory of the projectile.
U.S. Pat. No. 4,905,602 (Buckland) discloses a spin-damped training projectile, which has an array of spin-damping fins mounted on the nose of the projectile.
Ranges for testing the trajectory of large caliber ammunition require a great deal of area for obvious safety reasons. A typical range for a 25-mm projectile has a length of approximately 14-km because projectiles of 25-mm typically travel a distance of 12-km. These distances change depending on the size of the projectile. The larger projectiles require a proportionally larger area. Many ordnance applications, i.e., target practice rounds, require projectiles to satisfy two conflicting objectives: 1) achieve a high performance flat trajectory to a specified range and 2) abruptly decelerate and thereby not exceed a specified range limit. Conventional spin stabilized projectiles, due to their pointed cylindrical shape, are severely limited in the degree to which they can satisfy these two conflicting requirements.
The problem is that high initial velocities result in excessively long carry ranges; or alternatively, if the specified range limitation is met, the initial trajectory performance is inadequate.
The present invention solves this problem by providing a training projectile with a roll damping augmentation section that causes the projectile to become gyroscopically unstable after a traveling a predetermined distance. The gyroscopically unstable trajectory causes the projectile to begin high yaw and thereby reduces the distance the projectile will ultimately travel.
This invention relates to a projectile that achieves a flat trajectory to a specified predetermined distance and upon reaching that distance abruptly becomes gyroscopically unstable. Accordingly, one embodiment is drawn to a projectile having an ogival nose portion; a posterior portion; and a midportion.
The midportion includes a longitudinally extending roll damping augmentation section disposed in a recess and extending outwardly no more than approximately the depth of the recess. The roll damping augmentation section has flats of flutes defining grooves which interact with oncoming air causing the projectile to become gyroscopically unstable at a predetermined range and continuously gyroscopically unstable thereafter.